The present invention relates to an apparatus for producing rollers covered with layers of elastic silicone-based material.
Rollers made of silicone-based material have long been produced and used in printing by providing a matrix on their perimetric surface and by using the elasticity of their material to compensate for any microscopic bumps of the surfaces to which the print is to be applied.
Several other fields have long used rollers of various sizes which must have in common the characteristic of having an outer surface that is absolutely free from imperfections and is somewhat flexible to spontaneously adapt to the complementary surfaces with which they make contact; this is the case, for example, of rollers used as matrixes to decorate flat surfaces of products such as ceramic tiles.
Another field in which this type of roller is normally used is transport and conveyance in machines equipped with precision mechanics, such as photocopiers.
The above-mentioned decoration technique and precision in transport both require that the outer surfaces of the rollers on which the pattern to be printed is formed or on which the transported sheets rest, are smooth or indeed mirror-finished, so as to avoid any smudge or imperfection.
Accordingly, these rollers must have the smoothest possible lateral surface, with absolutely no imperfections and even mirror-finished and, as mentioned, substantially soft.
Said rollers are currently manufactured according to two basic methods: a first one consists in applying to a solid supporting cylinder strips of silicone rubber which are subsequently vulcanized; the surface thus obtained is then ground. A second process consists in pouring liquid degassed silicone into an openable cylindrical mold in which a support is placed; this is followed by a step for grinding the manufactured product.
However, both of the above described processes have drawbacks; in the first case it is impossible to obtain a surface that is sufficiently smooth, and mirror-finished; in addition said process requires onerous manual grinding operations during which the flexibility of the surface cannot drop below a certain value.
In the second case, only a single-layer covering can be obtained, and grinding is still necessary to eliminate the burr that forms in the points where the mold parts join.
Hence in both cases it is necessary to follow the actual covering step with the grinding step, and this entails a considerable waste of time and labor that negatively affects the production costs of the finished product.
Furthermore, the level of perfect-on that can be achieved with said grinding is still inadequate for the particular intended use of said rollers.